Abstract |
A new polymorph of 1-(4-hydroxyphenyl)pentan-1-one (4 -hydroxyvalerophenone, HVP) was identified by using differential scanning calorimetry, hot stage microscopy, and X-ray powder diffraction. This novel crystal form (form II) was obtained by crystallization from melt. It has a fusion temperature of T (fus) = 324.3 +/- 0.2 K and an enthalpy of fusion Delta(fus) H (m) (o) = 18.14 +/- 0.18 kJ center dot mol(-1). These values are significantly lower than those observed for the previously known phase (form I, monoclinic, space group P2(1)/c, T (fus) = 335.6 +/- 0.7 K; Delta(fus) H (m) (o) = 26.67 +/- 0.04 kJ center dot mol(-1)), which can be prepared by crystallization from ethanol. The results here obtained, therefore, suggest that form I is thermodynamically more stable than the newly identified form II and, furthermore, that the two polymorphs are monotropically related. |